kevindonkleywood, it is an odd video, as the slope appears flat. Must be the filming angle, but still, odd. And no, no funny business done to my video. (Sorry I got distracted by the tent display part way through the exercises one though...)
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Pedantica wrote:
I don't understand this. I take lessons in a snowdome and get loads more than 5-10 minutes skiing per hour.
The fastest guys in the races at the weekend were getting down Hemel (through gates) in about 11 seconds and the very slowest 7yo took 25 seconds. The only person who took 30 seconds to ski from top to bottom fell over. So let's make it 30 seconds actual skiing on average per run , then even if you allow for a turn around of 3 mins - which is not hanging about at all - that makes about 10 mins per hour. A fast racer would get about 3-4 mins/hour if skiing fast - but that's still quite knackering.
As for the stimuli on the treadmill, maybe they need something like the i-Max experience to fool the mind that you really are moving. Remember how dodgy it feels when you're in a perfectly still cinema seat and you watch a PoV car chase or something like that.
The worry I'd have about the treadmill is that you get no centrifugal (or -petal) effects, so the balance in the turn would be very strange. Those who like knocking dry-slope skiing always point to the excessive knee angulation or falling onto the inside foot that can be encouraged by the lower speeds on dry-slopes vs either indoor or outdoor snow. I think used with care the treadmill could be useful for ironing out particular persistent problems, but to me seems likely to be even more prone to those criticisms of the plastic-fantastic .
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
I know someone who is a regular user of such a contraption (his wife works with my wife). I usually meet the guy 3-4 times a year, and each time I get to hear lots about this "fantastic" machine and how it perfects his technique. Two or three years ago we met while skiing in Val Gardena, I was there with a friend, he was there with 4 or 5 guys that know each other from training on the "wonderful machine". As it was a good snow year and it snowed almost every day the pistes were soft, uneven, a blast! For me and friend that is. For those guys it was "bad snow", "too uneven", they complained that the previous year it didn't snow for at least 2 weeks prior to their vacation, so all the slopes were covered in artificial snow 'smooth and nice".
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my concern is that there is no opportunity to get a real 'feel' for the skis, no opportunity to learn to manage the edge pressures and read the feedback from the ski. Afterall the feel of the skis is critical and that what tells you if you have good technique or you have something wrong.
Ronald, 's video is a more honest look at the system as it shows not just the front on view but an oblique view which is much better for observing how the skis are interacting with the mat (and has not had any 'funny business' done to the video). I have to agree with him it is a tool for learning, but my concern is that there is no opportunity to get a real 'feel' for the skis, no opportunity to learn to manage the edge pressures and read the feedback from the ski. Afterall the feel of the skis is critical and that what tells you if you have good technique or you have something wrong.
Looking at the turn shapes they are not nice rounded turns because if you turn the skis too far across the hill you will end up in a cartoon like splat.
I can control edge pressure, have a look at the exercise video where I choose when to apply pressure. Before that I am letting the skis drift along the edge of the carpet.
Different surface, different feel of the skis. Not all snow is equal, is it? By your definition skiing on plastic is not skiing either, as it has a very different feel from snow as well
You get an incredibly strong feedback from mistakes in technique. If you don't move both legs exactly as one you stem and step (or fall). On real snow this gets hidden very very well indeed. Mistime things and you get to save yourself in a snowplow (or fall). Again real snow hides those things extremely well. This is all due to the different interaction of skis and surface, and as long as you realize and understand that, I find this a powerful tool, as what I learn on the treadmill transfers back on real snow very easily.
sugardaddy wrote:
Nail. Head. Methinks
Totally missed the nail. The treadmill is a tool, absolutely not the only solution. I know plenty of skiers who only ever been on real snow and absolutely hate anything but flat corduroy. the skiers in your example are beginners, just like a real snow beginner...
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
Ronald, A plastic slope feels different to snow, yes that is true, but then fresh POW feels different to boilerplate The important thing is the forces acting on the skis are the same and the feedback the skiier is learning to read is vaild.
Skiing on a treadmill is a tool like you say but the forces acting on the skis and on your body are totally different. Yes you get feedback from mistakes but that is from mistakes in the technique needed to ski the machine not the technique needed to ski well on snow. Spending too long on the machine will just cause these machine techniques to become 'aquired' and may hamper further development on snow.
If you take a look at your first video your will see that your centre of mass is always directly above the centre of the base of support made by your two skis, this is because you are acting to be stable against the only force acting on your body namely gravity. Now inagine your body in motion on a real or plastic slope, you now have momentum and as you turn you will have to balance against the (virtual) centrifugal force created by your body turning with the arc of the skis. This results in a totally different feel and muscle movement to maintain stability and your centre of mass will have to move to the inside the turn, otherwise you will simply fall over.
Just out of interest what are the hourly costs for treadmill skiing? with and without instruction?
Skiing on a treadmill is a tool like you say but the forces acting on the skis and on your body are totally different
I'm really struggling with this!
When skiing down a fixed slope made from snow/dendix/whatever, gravity is the force pulling you down the slope, with the treadmill gravity is still the main force pulling you over the surface, the fact you never actually get to the bottom is irrelevant, the only difference in feel I can see would be the lack of wind noise.
So if the gravity effect is the same & you were to ski on this "with your eyes closed" it would feel no different to skiing down a fixed slope "with your eyes closed" except for the lack of wind feeling in your locks!
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
I pay less then 20 euro for an hours shared lesson in off season package deals. Highest price is Winter single hour 27.50, lowest is 40 lessons over a year at 599 euro. They don't offer anything without instruction.
I'm not sure there would be a lot more movement away from the centre of the skis at these speeds on real snow... It's by no means fast skiing (one of the proper limitations of this method indeed!) The speed the surface goes is comparable to taking about 20-25 seconds for a run at Hemel, which is by no means quick (see GrahamN )
gatecrasher, It doesn't feel dramatically different, other then the difference in surface.
Surface is slower then snow (much like dendix), Holds better edge then dendix, and even more then dendix resists dragging the ski towards the side of the engaged edge (even with little to no pressure)
After all it is free
After all it is free
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this is because you are acting to be stable against the only force acting on your body namely gravity. Now inagine your body in motion on a real or plastic slope, you now have momentum
Kevindonkleywood
So imagine you are skiing down for arguments sake a fixed dendix slope and someone decides to spray it with tar right in front of you, when you hit the tar you will feel that momentum throwing you forward over the front of your skis! Now imagine skiing with the aid of gravity down "or" on this treadmill and again someone throws tar in front of your path, as you hit it you will still get the "feeling" of being thrown forward the "feeling of momentum" yes you will end up very shortly in a heap at the top of the slope but the "feeling" of momentum will be the same! and as you say the feeling is the important thing here.
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gatecrasher, Please explain how you experience centrigugal and centripetal forces from your turns when your body is not moving? its not about the change in surface its about the forces acting on the body. Your body is stationary as it would be on any number of ski excercise machines.
In normal skiing you are balancing the resultant force from gravity and the centrifugal force (virtual) acting on your entire body this gives a resultant force with vector direction that increases with the speed of the skier. On the treadmill it does not matter how fast the mat is moving the force is still just garavity acting down. (on your body)
If you believe this to be incorrect please show me a skier making a fast turn using only inclination on the treadmill, they would simply fall over as there is no centrifugal force to balance against.
Quote:
Holds better edge then dendix
Im sorry but this is just nonsense if you hold an edge for a fraction of a second you are off the back! your edges are always skidding.
Ski the Net with snowHeads
Ski the Net with snowHeads
Quote:
when your body is not moving?
But they are moving? "across the slope" If you hope sideways without any forward movement then hop sideways back and keep doing it, you would have to "lean in" to prevent yourself from falling outwards, so the faster the mat is running and the steeper the pitch of the slope the faster the skiers movements can be from one side to the other, increasing the possibilities of the greater inside movement.
I agree with you this has its limits, a successful fast turn using only inclination on this would be difficult as with most dendix slopes, simply because the speed is a lot slower on both and to be honest, how many good skiers do you see skiing around like that? with purely inclination alone!! I'll keep those sort of antics for snow "maybe!"
Last edited by Ski the Net with snowHeads on Thu 21-07-11 0:06; edited 1 time in total
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
kevindonkleywood, If you go on their website there is a guy Funcarving on it! loads of inlination!! think they might have wound the lacky band up on it a bit though!
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Fattes13, There are many text book turns... not all of them involve mach 666 and using 300 feet of slope width.
Couldn't agree more but there are few turns that require you to lift your ski PM me and I will tell you who I am related to there may make sense for you
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
kevindonkleywood wrote:
gatecrasher, Please explain how you experience centrigugal and centripetal forces from your turns when your body is not moving? its not about the change in surface its about the forces acting on the body. Your body is stationary as it would be on any number of ski excercise machines.
In normal skiing you are balancing the resultant force from gravity and the centrifugal force (virtual) acting on your entire body this gives a resultant force with vector direction that increases with the speed of the skier. On the treadmill it does not matter how fast the mat is moving the force is still just garavity acting down. (on your body)
If you believe this to be incorrect please show me a skier making a fast turn using only inclination on the treadmill, they would simply fall over as there is no centrifugal force to balance against.
Quote:
Holds better edge then dendix
Im sorry but this is just nonsense if you hold an edge for a fraction of a second you are off the back! your edges are always skidding.
The body is not stationary, it is moved left and right by forces acting on the skis. You cannot accelerate the body from the feet if it is exactly above the source of the force. Therefor some lean by angulation/inclination is required. Not that dissimilar to snow.
The surface has more resistance to skidding then dendix (which does feel like skiing a rather slow moving icy surface). This what most people will describe as edge holding. The equivalent of "being thrown of the back" on snow is skiing across the slope for a prolonged time, which we never do in text book turns. Furthermore you can do clean carves on the surface (I have seen one of the teachers do it, just that I cannot do it doesn't mean its impossible) which is by definition a fully engaged edge and he's not being thrown off the back.
It is totally fine to be skeptic, but you're pushing to find reasons to dismiss the concept now.
Fattes13 wrote:
Quote:
Fattes13, There are many text book turns... not all of them involve mach 666 and using 300 feet of slope width.
Couldn't agree more but there are few turns that require you to lift your ski PM me and I will tell you who I am related to there may make sense for you
No turn on the treadmill requires you to lift the ski. Read more carefully in the thread: The reason you see me lift is nothing but a technical fault being revealed.
You know it makes sense.
You know it makes sense.
Quote:
turn on the treadmill requires you to lift the ski. Read more carefully in the thread: The reason you see me lift is nothing but a technical fault being revealed.
Have seen instructors there when it opend first teaching people to turn by lifting as a progression exercise (Not sure if it is still done)
In fact one of the instructiors who is an incredible skier and a super race coach (Currently not working there) Used it as his main method to teach people new to the surface including myself.
As above it is a great facility for absolute newbies to sking but for more advanced stuff I dont think it fits the bill. It gives no sensation of movment or changing terrain. The Only person I have ever seen ski on it properly is Brian B.
It is a usefull but limited tool for ski technique and as for engaging the edges it is impossible as the edges on all skis used on the surface have to be rounded INCLUDING CHEMMYS SHE WAS ASKED TO DE TUNE Her skis before using them on it. Which she did with good humour and grace to all accounts and purposes.
So if you have no edges on the skis it is impossible to engage them
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
Ronald, wrote
Quote:
the skiers in your example are beginners, just like a real snow beginner...
nope. These are people who have been skiing for about 10 years. The were skiing for about 3-4 years before they started training regularly on a "rug", and from what i saw it did them more harm than good (they ski quite well on the rug, but they're hopeless on snow)
Poster: A snowHead
Poster: A snowHead
I remember a good while ago seeing in a cycling magazine a photo of a bike on rollers. This was not an exercise trainer where the frame is clamped. Instead the bike was completely free and had to be 'ridden' to maintain balance.
The author showed the photo to an engineer friend who was interested in such things. "I bet that feels weird" he said. And, apparently, it certainly did. The physics is just different.
I can see a rug will be good at ironing out some skiing faults. It could probably help a boot fitter too. However, I certainly wouldn't want to rely on one for much of my training.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
Fattes13 wrote:
So if you have no edges on the skis it is impossible to engage them on real snow
There I corrected it for you.
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
^^^^^^ Explain the correction?
If you have no edges you can not engage them on any surface a rounded edge is a rounded edge on the Toilet Brush Dendix / Dutch Mat or Snow if your edges are not sharp you can not use them
Invest in 'Ultimate skiing' by Ron LeMaster and read up about skiing dynamics and the forces that act on you as you ski
That's very fine advice. Both editions of Le Master's book are brilliant
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
kevindonkleywood,
I don't think anyone is disputing what keeps you up in skiing (simple terms) the grey area is what's keeping these guys up if the only available forces-centrifugal etc. as you mention are not present.
Yep, think I'm done on this one too!
Feet up beer time!
After all it is free
After all it is free
Years ago I worked in a ski/outdoor shop in Leeds (Wilderness Ways on Eastgate, anyone remember it?).
We had a rolling carpet ski machine thingy installed for maybe 6 months, this would have been about 1983 I would guess. Iw was a lot smaller than the one in the videos above, but had two parallel bits of carpet to ski on, which (I think) could be controlled separately. Mini skis were used. I was not a skier at the time but did have a bit of a play on the thing, but as I'd never skied on snow I had nothing to compare it with.
Onto some physics. I'm pretty certain that stationary bikes on rollers remain upright because of the gyroscopic stabilising effect of the spinning wheels.
I do not believe there is any difference in the physics of skiing on a moving surface (a ski machine) compared to skiing on a stationary surface such as a mountain. That is, if we remove both the effects of air resistance and the different physical characteristics of the skiing surface. The essential elements are the same in both cases, the constant effect of gravity, the relative speed of the skier compared to the surface, and changes to the skiers body shape to influence the behaviour of the ski. I'm reminded of the (incorrect) argument that it is easier to run on a treadmill than on a road because the runner is just going up and down rather than along. Again what matters is the relative speed of the runner to the treadmill surface. The relative speed of the runner to the fixed bit of the treadmill, the room around it, or indeed the earth through the cosmos are all irrelevant.
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Spud9, my physics education is a long way behind me, but as I understand it the key force which seems to apply in skiing is the centripetal (often referred to as centrifugal) force which builds up as a result of your angular momentum as you make turns. As far as I can make out this is going to be extremely limited when you are mostly stationary on the treadmill, so anything which involves learning to tip the skis on to their edges and balancing on them is going to be difficult because of the (lack of) forces involved. Just thinking about the coaching plans we use for our clinics at Hemel and I would struggle to teach them on a system like that. Also, how forgiving is this system when skiers make mistakes or fail to do what they are trying to do? It's rare that anyone I teach gets a new drill exactly right first time. Will the treadmill spit them out at the top for even minor mistakes?
Having said that, any skiing is better than no skiing IMO, even if the system isn't a perfect replication of what we do in the mountains.
Ski the Net with snowHeads
Ski the Net with snowHeads
rob@rar, Firstly, you of course know far more about how skis work, and the interaction between skis, ski surface and the body than I do, but i think my point still stands. The centripetal/centrefugal forces that build up while turning are caused by the interaction of the body with the skis and the ski surface, these will happen whether or not the skier is moving relative to the outside environment or not, but what is important is the relative speed of the skis/skier across the ski surface. What I'm saying is that it does not matter whether the ski surface is stationary or moving (providing the ski surface is moving at a constant speed in a straight line). A little thought experiment; put the ski machine on a (rather large) train. The turning forces applied by the skier to the skis will remain the same whether the train is going forward at 100 mph, backwards at 100 mph or is stationary.
Another thought experiment. Imagine two very large warehouses. One is filled with a huge rolling carpet ski machine, the second one has a fixed slope made of the same material. It's very dark in both warehouses. Plonk a skier with a headtorch in one or other of the warehousesand set them off skiing.All the skier can see is the ski surface immediately around themselves as he/she sets off skiing. I contend that the skier would not know whether they were on a moving carpet or on a fixed slope right up to the point where they smashed their face into the wall at the bottom of the fixed slope.
You are right about the ski machines being intolerant of mistakes; an abrupt slow down will rapidly deposit the skier over the back of the machine.
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
Quote:
Yep, think I'm done on this one too!
Feet up beer time
Ok so I lied & the beer ran out!
Spud9,
Quote:
The turning forces applied by the skier to the skis will remain the same whether the train is going forward at 100 mph, backwards at 100 mph or is stationary.
Obviously I totally agree with this!
Wanting to keep it simple but there is another element to all of this that "is" present in both examples (mountain vs treadmill) and without it centripetal force would not exist
Answers on a postcard please
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
Oh god I feel a 'virtual bump' type threadline resurfacing. I have no problem with this as a training tool but:
You the skiier have NO forward velocity and you the skiier have no angular momentum. What you do have is a lateral acceleration (from side to side) caused by the vector of the skis force that is not acting to counter gravity pulling you down the slope.
Because you have no angular momentum (because you have no angular velocity- You are stationary on the treadmill) you will experience NO centrifugal(centripital) forces these are only generated when a body has an angular momentum, the forces being tangental to the curve. You are not going round a curve (look at the video) you are simply going backwards and forwards, if you did have any angular momentum you would fly off the treadmill beacause your edges are not engaged with the surface you are slipping all the time your body would fly off at a tangent to the curve (which you dont have).
Your skis are not carving they are slipping, your body is NOT experiencing the forces you would experience on a slope when your body actually had an angular velocity.
Because you are experiencing a very different set of forces on your whole body if you train on the treadmill for too long you will have a lot of work to unlearn the habits once you get on the hill.
If you look at Chemmy skiing you can see that she is struggling because the experience is alien to her, the forces and the feelings are different! now will someone please suggest that this is because she has poor technique
At the end of the day it depends what you want out of your skiing, I know I have a long way to go with mine but I do not believe that treadmill time will do anything but damage to my already ropey technique.
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
So if you're just off somewhere snowy come back and post a snow report of your own and we'll all love you very much
Quote:
without it centripetal force would not exist
Answers on a postcard please
Here’s another example of “it” in action.
Her mass is definitely inside of her feet, she has “no” forward momentum, there is no centripetal force and she is “not” falling over.
She is using "it" in the same way as all skiers do including the treadmill ones!
gatecrasher, is that thing on rubber bands? What is stopping the trolley she's on from flying off sideways? From a quick glance it looks like the rubber bands are pulling the trolley towards the centre of the track she's on (a perfect analogy for centripetal force) and she is balancing against that force by having her centre of gravity inside her base of support, just like a skier on the mountain would do. This is completely different from the treadmill as there is only a very small centripetal force acting on the skier as there is almost no angular momentum. I think.
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
kevindonkleywood wrote:
Oh god I feel a 'virtual bump' type threadline resurfacing. I have no problem with this as a training tool but:
You the skiier have NO forward velocity and you the skiier have no angular momentum. What you do have is a lateral acceleration (from side to side) caused by the vector of the skis force that is not acting to counter gravity pulling you down the slope.
Because you have no angular momentum (because you have no angular velocity- You are stationary on the treadmill) you will experience NO centrifugal(centripital) forces these are only generated when a body has an angular momentum, the forces being tangental to the curve. You are not going round a curve (look at the video) you are simply going backwards and forwards, if you did have any angular momentum you would fly off the treadmill beacause your edges are not engaged with the surface you are slipping all the time your body would fly off at a tangent to the curve (which you dont have).
Yes you do have angular momentum. Momentum is mass multiplied by velocity. Mass is (pretty much) fixed, but what does 'velocity' mean? As everything in the universe is in constant motion 'velocity' can only mean speed compared to some other object. The momentum of any object will vary depending on where you are measuring it from. Imagine standing on a train travelling at 60 mph, then throwing a cricket ball at 60 mph in the direction 'backwards' down the carriage. From the point of view of an observor outside the train the cricket ball will have zero momentum. So far as he can see the ball is stationary (in the horizontal plane) so it has zero momentum (mass x zero velocity). On the other hand someone on the train who tries to catch the ball will get the full benefit of the cricket ball's momentum of mass x velocity of 60mph.
When skiing on a moving carpet the angular momentum of the skier, from the skiers point of view, is given by the mass multiplied by his speed relative to the surface he's skiing on. It makes no difference if the skier is 'stationary' (compared to what?) and the skier is moving or if the skier is moving and the slope is stationary.
So, yes the skier has both angular velocity and angular momentum from his point of view, and that is the only point of view that matters.
Poster: A snowHead
Poster: A snowHead
Spud9 wrote:
The centripetal/centrefugal forces that build up while turning are caused by the interaction of the body with the skis and the ski surface,
I'm happy to be corrected, but I don't think that is right. I don't think friction and centripetal force are linked.
An alternative thought experiment: imagine a bike on one of those training treadmills/rollers, cycling at 50mph. Can the cyclist "lean in" to an imaginary turn in the same way as a cyclist doing 50mph going around a real bend in the road? I don't think so. The cyclist in the treadmill would simply fall over, even though there is a reasonable comparison between the interaction of the wheels on the treadmill with the wheels on the road surface.
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
kevindonkleywood, I have no experience but my intuitive view aligns closer to yours and rob's. I can't see how ski time is bad time so I'm not sure the experience is damaging (other than in an ego crushing way), as at least you'd learn how to be precise in the sort of simultaneous engagement/release encouraged but a big caveat would have to be that this is only one aspect of the feel of turn and a particular type of turn at that. I won't be rushing to my nearest rolling carpet centre.
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
Spud9 wrote:
So, yes the skier has both angular velocity and angular momentum from his point of view, and that is the only point of view that matters.
The skier has (almost) no angular momentum on the treadmill because they are not rotating around an axis/following a curved path.
... I'm not sure the experience is damaging (other than in an ego crushing way), as at least you'd learn how to be precise in the sort of simultaneous engagement/release encouraged but a big caveat would have to be that this is only one aspect of the feel of turn and a particular type of turn at that.
I think that's right. Useful, but limited would be my summary. Good for timing, coordination, managing (some) body movements, good CV workout, etc, but limited use for other things.
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
rob@rar wrote:
Spud9 wrote:
The centripetal/centrefugal forces that build up while turning are caused by the interaction of the body with the skis and the ski surface,
I'm happy to be corrected, but I don't think that is right. I don't think friction and centripetal force are linked.
An alternative thought experiment: imagine a bike on one of those training treadmills/rollers, cycling at 50mph. Can the cyclist "lean in" to an imaginary turn in the same way as a cyclist doing 50mph going around a real bend in the road? I don't think so. The cyclist in the treadmill would simply fall over, even though there is a reasonable comparison between the interaction of the wheels on the treadmill with the wheels on the road surface.
I think your cyclist on a treadmill experiment is a good one. Rollers are strange things where a cyclist stays upright because of the gyroscopic forces generated by the spinning bike wheels, so lets concentrate on a treadmill (a bigger version of the running treadmills you get in gyms). I agree that there is a reasonable comparison between cycling on such a treadmill and cycling on the road, but i think you are incorrect in saying that the cyclist cannot lean into the turn. I suggest that the cyclist can lean into the turn and remain upright because the forces acting on the cyclist are exactly the same as those acting on a cyclist riding on a road. If the treadmill was long enough and wide enough the cylict could then contiue cycling happily in the new direction until they ran out of surface either at the side or at the back of the treadmill.
Spud9, on that large treadmill would the cyclist be travelling in a straight line or following a curved path?
Then you can post your own questions or snow reports...
Then you can post your own questions or snow reports...
kevindonkleywood, rob@rar, having originally said that the major problem with this was the lack of centripetal forces required from the skier, I've now changed my mind and amd much more in agreement with Spud9.
Spud9's argument about velocities being entirely relative is correct. It makes no difference to the effect of gravity on us whether we are stationary with respect to the earth's surface or falling at 100mph towards it, or in any other direction (ok, other than the inverse-square law changes as we change the separation between our CoM and its ). The motion we see on the carpet therefore looks different to us as we are effectively moving down the slope at a similar rate to the skier - something we're not all that familiar with (but try watching a racer from the top of a course when the distance effect is much reduced by visual foreshortening). And yes there are the same angular momentum changes as you go through the turn.
The crux here though is that the skier allows themselves to move down the carpet while in the fall-line, and be carried further up the hill when skiing across it. We do see that to a small degree in Ronald's vid, but he's not doing it much because he's pivoting his turns quite a lot and spending very little time in the fall-line. So I think that's a strong misdirector towards kevindonkleywood's argument, which I now entirely reject. Rob, yes his turns are making a curved path on the carpet, but just a bit too quick at the apex. There is a strong enough psychological disincentive to keeping your skis pointing directly downhill and you feel yourself picking up speed when on an open slope, but that must be much greater when you see the bottom of the carpet coming back up to you. Hence my comment earlier about having some kind of I-MAX visual surround to get the psychological input more nearly correct. You could also go to the next step of putting it in front of a wind-machine to get the air resistance effect as well .
I think there could still be quite a problem in that you are getting only low speeds, and hence the forces are quite low. How much speed control does the coach have over the speed of the carpet, and its slope, while the skier is skiing on it - I would see that you would want to start a training run slowly, then pick up quite a lot of speed if you wanted to get into a carving/angulation/inclination exercise, then slow down again to come to a safe stop - just as you would on a normal training run. The advantage here is that the trainer can set up the slope for exactly the "terrain" that the trainee needs at their particular level of development, or particular skill that is being worked on. You'd also want something like that for safety - as when the trainee gets it wrong their speed would change quite rapidly (normally drop...but could increase if it were some kind of edging exercise), so the carpet speed would have to change to match that.
After all it is free
After all it is free
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If the treadmill was long enough and wide enough the cylict could then contiue cycling happily in the new direction until they ran out of surface either at the side or at the back of the treadmill.
Spud9, Was just writing this but you beat me to it! cool!
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You'll get to see more forums and be part of the best ski club on the net.
kevindonkleywood,
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Oh god I feel a 'virtual bump' type threadline resurfacing
Yeah but you love it really!
Ski the Net with snowHeads
Ski the Net with snowHeads
GrahamN wrote:
Rob, yes his turns are making a curved path on the carpet, but just a bit too quick at the apex.
But the extent of the curved path is quite limited? So the centripetal forces are relatively low? That's my point, rather than centripetal forces are absent.
FAQ
Poster: A snowHead
, then even if you allow for a turn around of 3 mins - which is not hanging about at all - that makes about 10 mins per hour. A fast racer would get about 3-4 mins/hour if skiing fast - but that's still quite knackering.
PM me and I will tell you who I am related to there may make sense for you
